Correct answer: B
Cooling curve is the plot of temperature versus time as the sample is allowed to cool. In a cooling curve, we start at a temperature greater than the boiling point. At this temperature, the sample is in gaseous state. At the boiling point, there is no change in temperature as the gaseous and liquid states are in equilibrium. As the temperature reduces further, the liquid starts to condense and at the melting point of the sample the liquid undergoes phase transition to solid state. At the melting temperature, a second plateau is observed as the temperature remains unchanged. At temperatures below the melting point, the sample exists as a solid.
So from the curve, the second plateau is observed at around -111
. This point represents the phase transition from liquid to solid state.
Answer:
physical change because the gaseous water is chemically the same as the liquid
Explanation:
Matter can be defined as anything that has mass and occupies space. Any physical object that is found on earth is typically composed of matter. Matter are known to be made up of atoms and as a result has the property of existing in states.
Generally, matter exists in three (3) distinct or classical phases and these are; solid, liquid and gas.
A physical change can be defined as a type of change that only affects the physical form of a chemical substance (matter) without having any effect on its chemical properties. Thus, a physical change would only affect the physical appearance and properties of a chemical substance (matter) but not its chemical properties.
This ultimately implies that, a physical change result in a change of matter from one form or phase (liquid, solid or gas) to another without a corresponding change in chemical composition.
Hence, the boiling of water is considered to be a physical change because the gaseous water is chemically the same as the liquid i.e there isn't any changes in chemical composition of water when boiling.
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Answer: Moles of hydrogen required are 4.57 moles to make 146.6 grams of methane, 
.
Explanation:
Given: Mass of methane = 146.6 g
As moles is the mass of a substance divided by its molar mass. So, moles of methane (molar mass = 16.04 g/mol) are calculated as follows.
The given reaction equation is as follows.
This shows that 2 moles of hydrogen gives 1 mole of methane. Hence, moles of hydrogen required to form 9.14 moles of methane is as follows.
Thus, we can conclude that moles of hydrogen required are 4.57 moles to make 146.6 grams of methane, .
Answer:
$1246.90
Explanation:
Since the bike lost 
% of it's value and it now currently at $
, we have to do 20% * $1039 to find the amount of money lost. 20%*1039=207.8. We have to add it up to find the original value so 1039+207.8=$1246.8
